My query is like this
select 5 from mytable_name;
Then the output is like column name 5 and the value is 5 printing as many max number of rows exists in that table.
Can anybody tell the reason why this query is working like this?
Can anybody tell the reason why this query is working like this?
You are selecting a string literal value '5' for each row in your table:
select 5 from mytable_name;
And this works fine. Because in the SELECT statement you can select:
Column reference,
Literal value like in your case.
Function.
value expression.
Select expression.
As defined by the standard SQL1:
Update:
However, If you have a column with a name is a number like in your case, you have to escape it in order to select the values in it like so:
SELECT `143` FROM Table1;
This will select all the rows in the column 143.
But, this:
SELECT 143 FROM Table1;
Will select the string literal 143 for each row found in the table.
Note that: If possible, try not to name these columns this way, it is recommended and a best practice, not to do this.
SQL Fiddle Demo
Update 2:
Note that, if you select 143 or '143', or even "143" this will select the literal value 143 not the column date. The following are the same:
SELECT 143 FROM Table1;
SELECT '143' FROM Table1;
SELECT "143" FROM Table1;
All these SELECTs won't select the data in the column, They will select the literal value 143 not the column data. See this demo:
Demo
You have to escape the column name with the two:
``
Like this:
SELECT `143` FROM table1;
Not:
SELECT '143' FROM table1'
Like what I did here:
The right Demo
1Image From: SQL Queries for Mere Mortals
from mytable
will select all rows from your table if there is no where condition that shrinks that result. and
select 5
will select the constant number 5 for every record. If you use a column name in the select part then that value will be selected for every record.
The DB engine will name the result 5 because it automatically generates a column name and 5 is the logical name for that.
You want 'SELECT * FROM mytable_name LIMIT 0,5' perhaps?
Since you don't have anything in your where clause, it is selecting all the rows from your table. The fact that you don't select any of the columns is irrelevant - you'll still get a result for each row in the table.
With the command select 5 ... you are viewing a fixed value. Same thing you run the following command: select "test", you will be displaying a fixed string.
Using ... from mytable_name you're looking for all record of this table.
With this we can conclude that for each record in the table mytable_name shows you the fixed value "5".
Related
I have tried to select something with SQL, and I've a problem with it.
What I want:
SQL SELECT * FROM table WHERE ? = '5';
Select everything which = 5, BUT not specify from which column.
Example:
From this ""database"", you should receive the 1st and the last row.
Is that possible?
You have to list the columns but you can use in. The where clause looks like:
where 5 in (price, height)
Note: This assumes that the columns have the same type. You could get type conversion errors if they are not.
Also, given the names of the column and the data, I assume that the columns are stored as numbers. Hence, I dropped the single quotes around 5. If they are really strings, then use the single quotes.
you need to add a condition to your query with or keyword so if any of them match the row will be shown as a result
SELECT * FROM tablename WHERE price =5 or height= 5
better you list your columns by name instead of using * after SELECT
I have used below mysql query for fetching data:
select *
from tableName
where tableName.field_type='22'
and tableName.field_id NOT LIKE(select aField_id
from TableName 02 where status !='Active')
I am getting error
1242 - Subquery returns more than 1 row
can you let me know what wrong in this query
select * from tableName
where tableName.field_type='22'
and
tableName.field_id
NOT IN(select aField_id from TableName where status !='Active')
Use not in in place of not like. Not in is for comparison of column with a set of values. not like is for comparison of column with a single value or pattern. Your subquery in returning more than one rows. not like can't handle that.
Like deals with only one input. So you should use IN in place of LIKE.
Is there a way to get a column name from table where all values in this column are the same!
Example! IF i would there would be a such a code it would return answer 'Works'
Table1
ID Name Works
1 Andre Yes
2 John Yes
3 Stewart Yes
I don't know if the columns of the table are known. If not, you could be able to get them by:
desc Table1;
or if you are using higher version of MySQL, you could use:
select column_name from information_schema.columns where table_schema='your_schema' and table_name='Table1';
Then you try the following statement with parameters #column being replaced with the column names retrieved from the above statement:
select count(*) from (select count(*) as c from Table1 as t group by t.#column) as sub;
If the result is 1, the column is what you want. The result means how many distinct values this column has.
I suppose you will have to use a kind of programming language or stored procedure. You are not likely being able to achieve that with one single SQL statement.
I'm not sure if it's possible to run from MySQL itself but you can do this from your scripting engine.
You can run a loop on each column and do a query:
SELECT
COUNT(DISTINCT column_name)
FROM table_name;
And see you get 1 record in the results
I'm trying to run a SQL SELECT statement against a column that is of type SET. The table is called myTable and the columns in myTable are called base_props and names. The base_props column is of type SET. The values in base_prop are vb,nt, cnt,poss and loc. So I would like to SELECT entries from the column 'name' where base_props have both the values, vb and poss. The results I'm looking to get may have values other than just vb and poss. So to be clear I would like to select all entries that have the values vb and poss regardless if they have other values as well. I've tried the following SQL queries but I can't get the desired results.
SELECT name from myTable WHERE base_props = 'vb' AND base_props = 'poss'
That query returns an empty result set. I've tried using FIND_IN_SET() and IN() but I couldn't get anywhere with that. I've written SQL statements before but never had to deal with columns that are type SET. Any help is appreciated.
The only thing I can come up with is using the LIKE keyword:
SELECT name FROM myTable WHERE (base_props LIKE '%vb%' AND base_props LIKE '%poss%');
This will make sure both vb and cnt are in the base_props column. Of course you can use cnt, nt and loc in there, or any number of base_props values in the sql, just add more AND statements.
OR as a deleted answer by samitha pointed out, you can use FIND_IN_SET:
SELECT name from myTable WHERE FIND_IN_SET('vb', base_props) AND FIND_IN_SET('poss', base_props);
Comment (by spencer7593): "both of these work, but there is a slight difference. The LIKE operator will actually match any member that includes the search string anywhere in a term; the FIND_IN_SET function will only match an exact member. It's also possible to search for members in set by the order they appear in the SET definition, using the MySQL BITAND operator: for example, to match the 1st and 4th members of the set: WHERE base_props & 1 AND base_props & 8". So for example, if you have 'a' and 'aaa' in your set, then using the LIKE "%a%" method will also return rows containing 'aaa'.
Conclusion: use the FIND_IN_SET solution since it will work for all cases.
FIND_IN_SET return index, Try this
SELECT name from myTable WHERE FIND_IN_SET(base_props, 'vb') > 0 AND
FIND_IN_SET(base_props, 'poss') > 0
I have a table named table and one of rows in table has a with a value column like this: 6,7,8,9
I want to select this row and this is the code I expected to work:
SELECT * FROM table WHERE 8 IN (column)
It doesn't work. However the code which works confuses me:
SELECT * FROM table WHERE 6 IN (column)
I tried with several values and found out that only the first element of the list is working.
How can this be?
Because you are comparing number with string. 6,7,8,9 cast to number will be 6, so it will be true when do 6 IN (column).
You need to use FIND_IN_SET function:
SELECT * FROM `table` WHERE FIND_IN_SET(8, `column`);